Touch sensors which detect the presence of a finger at their surface by the resulting capacitance variation are known. Such sensors, usually called “capacitive touch-sensitive sensors”, are for example used in displays, keyboards, and touch pads of computers, of so-called “smartphones”, or of tablets.
Such sensors usually comprise at least two electrodes formed at the surface of a dielectric layer, and defining with said layer a capacitance of known value. This capacitance forms, with a finger located close to or in contact with the sensor, a capacitive system having a capacitance different from that of the sensor alone. The measurement of the capacitance difference resulting from the presence of a finger, and its comparison with the capacitance of the sensor alone, thus enables to detect the finger.
However, the detection of the presence of a finger close to or in contact with the sensor is generally insufficient to characterize a user's action. Indeed, the user usually intends to start an action by means of a display, of a keyboard, or of a touch pad by effectively pressing the latter. Now, although capacitive sensors “record” a capacitance variation in the presence of a finger, they do not enable to detect the pressure exerted by the latter.